1. Field of the Invention
The present invention relates to a backlight unit incorporating a light emitting diode (LED) as a light source, and more particularly, to a slimmer backlight unit which is reduced in thickness, weight and manufacturing costs and improved in heat releasing efficiency.
2. Description of the Related Art
A light emitting diode (LED) converts an electrical signal into an infrared ray, visible light or other form by using properties of a compound, and is used for a signal transmitting/receiving device.
In general, the LED is utilized in electronic home appliances, remote controllers, display boards, displays and various kinds of automation devices. The LED is largely broken down into an Infrared Emitting Diode (IRED) and a Visible Light Emitting Diode (VLED).
Such an LED is adopted adequately for e.g., the electronic home appliances and display boards depending on intensity of light outputted therefrom. A smaller and slimmer trend in the telecommunication device has given rise to a surface mount device, which is directly mountable on a printed circuit board.
Also, with broader applicability of the LED, higher brightness is increasingly required especially in daily appliances such as electric lights and rescue signal lights. Thus recently a high output LED is in wide use. But this high output LED generates heat significantly and accordingly when mounted in e.g., a backlight unit with a small mounting area, heat from the LED fails to be released properly, thereby undermining efficiency of the product or causing malfunction. To overcome such a problem, recently a backlight unit with excellent heat releasing properties has been conceived.
With reference to the accompanying drawings, a conventional backlight unit will be explained in detail.
FIG. 1 is an exploded perspective view illustrating the conventional backlight unit and FIG. 2 is a cross-sectional view illustrating the conventional backlight unit.
As shown in FIGS. 1 and 2, the conventional backlight unit includes a bottom plate 10 for mounting each part therein, a Metal Core Printed circuit Board (MCPCB) 20 disposed on the bottom plate, an LED package 30 mounted on the MCPCB 20 and an optical sheet 40 for processing light generated from the LED package 30.
Also, the MCPCB 20 has an electrically-conducting pattern 22 formed thereon. The LED package 30 is connected to the pattern 22 by a lead frame 32. Furthermore, a heat conducting adhesive 50 is disposed between an underside surface of the LED package and a top surface of the MCPCB 20 to fix the LED package.
Heat generated from the LED package 30 is transferred to the MCPCB 20 through the heat conducting adhesive 50 and then again to the bottom plate 10 so as to be released outward. Here, the MCPCB 20 is made of a high heat conductivity metal, thereby releasing heat generated from the LED package 30 to the outside faster. This prevents heat generated from the LED package 30 from degrading efficiency of the product or causing malfunction.
Such an MCPCB 20 transfers heat from the LED quickly. On the other hand, the MCPCB 20 is relatively thick and heavy, thereby adding thickness and weight to an overall backlight unit. In addition, the MCPCB 20 is expensive, thereby increasing manufacturing costs of the backlight unit.